Home | History | Annotate | Download | only in gesture_detection 
      1 // Copyright 2014 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "ui/events/gesture_detection/scale_gesture_detector.h"
      6 
      7 #include <limits.h>
      8 #include <cmath>
      9 
     10 #include "base/float_util.h"
     11 #include "base/logging.h"
     12 #include "ui/events/gesture_detection/motion_event.h"
     13 
     14 using base::TimeDelta;
     15 using base::TimeTicks;
     16 
     17 namespace ui {
     18 namespace {
     19 
     20 // Using a small epsilon when comparing slop distances allows pixel perfect
     21 // slop determination when using fractional DPI coordinates (assuming the slop
     22 // region and DPI scale are reasonably proportioned).
     23 const float kSlopEpsilon = .05f;
     24 
     25 const int kTouchStabilizeTimeMs = 128;
     26 
     27 const float kScaleFactor = .5f;
     28 
     29 }  // namespace
     30 
     31 // Note: These constants were taken directly from the default (unscaled)
     32 // versions found in Android's ViewConfiguration.
     33 ScaleGestureDetector::Config::Config()
     34     : span_slop(16),
     35       min_scaling_touch_major(48),
     36       min_scaling_span(200),
     37       min_pinch_update_span_delta(0) {
     38 }
     39 
     40 ScaleGestureDetector::Config::~Config() {}
     41 
     42 bool ScaleGestureDetector::SimpleScaleGestureListener::OnScale(
     43     const ScaleGestureDetector&, const MotionEvent&) {
     44   return false;
     45 }
     46 
     47 bool ScaleGestureDetector::SimpleScaleGestureListener::OnScaleBegin(
     48     const ScaleGestureDetector&, const MotionEvent&) {
     49   return true;
     50 }
     51 
     52 void ScaleGestureDetector::SimpleScaleGestureListener::OnScaleEnd(
     53     const ScaleGestureDetector&, const MotionEvent&) {}
     54 
     55 ScaleGestureDetector::ScaleGestureDetector(const Config& config,
     56                                            ScaleGestureListener* listener)
     57     : listener_(listener),
     58       focus_x_(0),
     59       focus_y_(0),
     60       curr_span_(0),
     61       prev_span_(0),
     62       initial_span_(0),
     63       curr_span_x_(0),
     64       curr_span_y_(0),
     65       prev_span_x_(0),
     66       prev_span_y_(0),
     67       in_progress_(0),
     68       span_slop_(0),
     69       min_span_(0),
     70       touch_upper_(0),
     71       touch_lower_(0),
     72       touch_history_last_accepted_(0),
     73       touch_history_direction_(0),
     74       touch_min_major_(0),
     75       touch_max_major_(0),
     76       double_tap_focus_x_(0),
     77       double_tap_focus_y_(0),
     78       double_tap_mode_(DOUBLE_TAP_MODE_NONE),
     79       event_before_or_above_starting_gesture_event_(false) {
     80   DCHECK(listener_);
     81   span_slop_ = config.span_slop + kSlopEpsilon;
     82   touch_min_major_ = config.min_scaling_touch_major;
     83   touch_max_major_ = std::min(config.min_scaling_span / std::sqrt(2.f),
     84                               2.f * touch_min_major_);
     85   min_span_ = config.min_scaling_span + kSlopEpsilon;
     86   ResetTouchHistory();
     87 }
     88 
     89 ScaleGestureDetector::~ScaleGestureDetector() {}
     90 
     91 bool ScaleGestureDetector::OnTouchEvent(const MotionEvent& event) {
     92   curr_time_ = event.GetEventTime();
     93 
     94   const int action = event.GetAction();
     95 
     96   const bool stream_complete =
     97       action == MotionEvent::ACTION_UP ||
     98       action == MotionEvent::ACTION_CANCEL ||
     99       (action == MotionEvent::ACTION_POINTER_DOWN && InDoubleTapMode());
    100 
    101   if (action == MotionEvent::ACTION_DOWN || stream_complete) {
    102     // Reset any scale in progress with the listener.
    103     // If it's an ACTION_DOWN we're beginning a new event stream.
    104     // This means the app probably didn't give us all the events. Shame on it.
    105     if (in_progress_) {
    106       listener_->OnScaleEnd(*this, event);
    107       ResetScaleWithSpan(0);
    108     } else if (InDoubleTapMode() && stream_complete) {
    109       ResetScaleWithSpan(0);
    110     }
    111 
    112     if (stream_complete) {
    113       ResetTouchHistory();
    114       return true;
    115     }
    116   }
    117 
    118   const bool config_changed = action == MotionEvent::ACTION_DOWN ||
    119                               action == MotionEvent::ACTION_POINTER_UP ||
    120                               action == MotionEvent::ACTION_POINTER_DOWN;
    121 
    122   const bool pointer_up = action == MotionEvent::ACTION_POINTER_UP;
    123   const int skip_index = pointer_up ? event.GetActionIndex() : -1;
    124 
    125   // Determine focal point.
    126   float sum_x = 0, sum_y = 0;
    127   const int count = static_cast<int>(event.GetPointerCount());
    128   const int unreleased_point_count = pointer_up ? count - 1 : count;
    129   const float inverse_unreleased_point_count = 1.0f / unreleased_point_count;
    130 
    131   float focus_x;
    132   float focus_y;
    133   if (InDoubleTapMode()) {
    134     // In double tap mode, the focal pt is always where the double tap
    135     // gesture started.
    136     focus_x = double_tap_focus_x_;
    137     focus_y = double_tap_focus_y_;
    138     if (event.GetY() < focus_y) {
    139       event_before_or_above_starting_gesture_event_ = true;
    140     } else {
    141       event_before_or_above_starting_gesture_event_ = false;
    142     }
    143   } else {
    144     for (int i = 0; i < count; i++) {
    145       if (skip_index == i)
    146         continue;
    147       sum_x += event.GetX(i);
    148       sum_y += event.GetY(i);
    149     }
    150 
    151     focus_x = sum_x * inverse_unreleased_point_count;
    152     focus_y = sum_y * inverse_unreleased_point_count;
    153   }
    154 
    155   AddTouchHistory(event);
    156 
    157   // Determine average deviation from focal point.
    158   float dev_sum_x = 0, dev_sum_y = 0;
    159   for (int i = 0; i < count; i++) {
    160     if (skip_index == i)
    161       continue;
    162 
    163     dev_sum_x += std::abs(event.GetX(i) - focus_x);
    164     dev_sum_y += std::abs(event.GetY(i) - focus_y);
    165   }
    166   // Convert the resulting diameter into a radius, to include touch
    167   // radius in overall deviation.
    168   const float touch_radius = touch_history_last_accepted_ / 2;
    169 
    170   const float dev_x = dev_sum_x * inverse_unreleased_point_count + touch_radius;
    171   const float dev_y = dev_sum_y * inverse_unreleased_point_count + touch_radius;
    172 
    173   // Span is the average distance between touch points through the focal point;
    174   // i.e. the diameter of the circle with a radius of the average deviation from
    175   // the focal point.
    176   const float span_x = dev_x * 2;
    177   const float span_y = dev_y * 2;
    178   float span;
    179   if (InDoubleTapMode()) {
    180     span = span_y;
    181   } else {
    182     span = std::sqrt(span_x * span_x + span_y * span_y);
    183   }
    184 
    185   // Dispatch begin/end events as needed.
    186   // If the configuration changes, notify the app to reset its current state by
    187   // beginning a fresh scale event stream.
    188   const bool was_in_progress = in_progress_;
    189   focus_x_ = focus_x;
    190   focus_y_ = focus_y;
    191   if (!InDoubleTapMode() && in_progress_ &&
    192       (span < min_span_ || config_changed)) {
    193     listener_->OnScaleEnd(*this, event);
    194     ResetScaleWithSpan(span);
    195   }
    196   if (config_changed) {
    197     prev_span_x_ = curr_span_x_ = span_x;
    198     prev_span_y_ = curr_span_y_ = span_y;
    199     initial_span_ = prev_span_ = curr_span_ = span;
    200   }
    201 
    202   const float min_span = InDoubleTapMode() ? span_slop_ : min_span_;
    203   if (!in_progress_ && span >= min_span &&
    204       (was_in_progress || std::abs(span - initial_span_) > span_slop_)) {
    205     prev_span_x_ = curr_span_x_ = span_x;
    206     prev_span_y_ = curr_span_y_ = span_y;
    207     prev_span_ = curr_span_ = span;
    208     prev_time_ = curr_time_;
    209     in_progress_ = listener_->OnScaleBegin(*this, event);
    210   }
    211 
    212   // Handle motion; focal point and span/scale factor are changing.
    213   if (action == MotionEvent::ACTION_MOVE) {
    214     curr_span_x_ = span_x;
    215     curr_span_y_ = span_y;
    216     curr_span_ = span;
    217 
    218     bool update_prev = true;
    219 
    220     if (in_progress_) {
    221       update_prev = listener_->OnScale(*this, event);
    222     }
    223 
    224     if (update_prev) {
    225       prev_span_x_ = curr_span_x_;
    226       prev_span_y_ = curr_span_y_;
    227       prev_span_ = curr_span_;
    228       prev_time_ = curr_time_;
    229     }
    230   }
    231 
    232   return true;
    233 }
    234 
    235 bool ScaleGestureDetector::IsInProgress() const { return in_progress_; }
    236 
    237 bool ScaleGestureDetector::InDoubleTapMode() const {
    238   return double_tap_mode_ == DOUBLE_TAP_MODE_IN_PROGRESS;
    239 }
    240 
    241 float ScaleGestureDetector::GetFocusX() const { return focus_x_; }
    242 
    243 float ScaleGestureDetector::GetFocusY() const { return focus_y_; }
    244 
    245 float ScaleGestureDetector::GetCurrentSpan() const { return curr_span_; }
    246 
    247 float ScaleGestureDetector::GetCurrentSpanX() const { return curr_span_x_; }
    248 
    249 float ScaleGestureDetector::GetCurrentSpanY() const { return curr_span_y_; }
    250 
    251 float ScaleGestureDetector::GetPreviousSpan() const { return prev_span_; }
    252 
    253 float ScaleGestureDetector::GetPreviousSpanX() const { return prev_span_x_; }
    254 
    255 float ScaleGestureDetector::GetPreviousSpanY() const { return prev_span_y_; }
    256 
    257 float ScaleGestureDetector::GetScaleFactor() const {
    258   if (InDoubleTapMode()) {
    259     // Drag is moving up; the further away from the gesture start, the smaller
    260     // the span should be, the closer, the larger the span, and therefore the
    261     // larger the scale.
    262     const bool scale_up = (event_before_or_above_starting_gesture_event_ &&
    263                            (curr_span_ < prev_span_)) ||
    264                           (!event_before_or_above_starting_gesture_event_ &&
    265                            (curr_span_ > prev_span_));
    266     const float span_diff =
    267         (std::abs(1.f - (curr_span_ / prev_span_)) * kScaleFactor);
    268     return prev_span_ <= 0 ? 1.f
    269                            : (scale_up ? (1.f + span_diff) : (1.f - span_diff));
    270   }
    271   return prev_span_ > 0 ? curr_span_ / prev_span_ : 1;
    272 }
    273 
    274 base::TimeDelta ScaleGestureDetector::GetTimeDelta() const {
    275   return curr_time_ - prev_time_;
    276 }
    277 
    278 base::TimeTicks ScaleGestureDetector::GetEventTime() const {
    279   return curr_time_;
    280 }
    281 
    282 bool ScaleGestureDetector::OnDoubleTap(const MotionEvent& ev) {
    283   // Double tap: start watching for a swipe.
    284   double_tap_focus_x_ = ev.GetX();
    285   double_tap_focus_y_ = ev.GetY();
    286   double_tap_mode_ = DOUBLE_TAP_MODE_IN_PROGRESS;
    287   return true;
    288 }
    289 
    290 void ScaleGestureDetector::AddTouchHistory(const MotionEvent& ev) {
    291   const base::TimeTicks current_time = ev.GetEventTime();
    292   DCHECK(!current_time.is_null());
    293   const int count = static_cast<int>(ev.GetPointerCount());
    294   bool accept = touch_history_last_accepted_time_.is_null() ||
    295                 (current_time - touch_history_last_accepted_time_) >=
    296                     base::TimeDelta::FromMilliseconds(kTouchStabilizeTimeMs);
    297   float total = 0;
    298   int sample_count = 0;
    299   for (int i = 0; i < count; i++) {
    300     const bool has_last_accepted = !base::IsNaN(touch_history_last_accepted_);
    301     const int history_size = static_cast<int>(ev.GetHistorySize());
    302     const int pointersample_count = history_size + 1;
    303     for (int h = 0; h < pointersample_count; h++) {
    304       float major;
    305       if (h < history_size) {
    306         major = ev.GetHistoricalTouchMajor(i, h);
    307       } else {
    308         major = ev.GetTouchMajor(i);
    309       }
    310       if (major < touch_min_major_)
    311         major = touch_min_major_;
    312       if (major > touch_max_major_)
    313         major = touch_max_major_;
    314       total += major;
    315 
    316       if (base::IsNaN(touch_upper_) || major > touch_upper_) {
    317         touch_upper_ = major;
    318       }
    319       if (base::IsNaN(touch_lower_) || major < touch_lower_) {
    320         touch_lower_ = major;
    321       }
    322 
    323       if (has_last_accepted) {
    324         const float major_delta = major - touch_history_last_accepted_;
    325         const int direction_sig =
    326             major_delta > 0 ? 1 : (major_delta < 0 ? -1 : 0);
    327         if (direction_sig != touch_history_direction_ ||
    328             (direction_sig == 0 && touch_history_direction_ == 0)) {
    329           touch_history_direction_ = direction_sig;
    330           touch_history_last_accepted_time_ = h < history_size
    331                                                   ? ev.GetHistoricalEventTime(h)
    332                                                   : ev.GetEventTime();
    333           accept = false;
    334         }
    335       }
    336     }
    337     sample_count += pointersample_count;
    338   }
    339 
    340   const float avg = total / sample_count;
    341 
    342   if (accept) {
    343     float new_accepted = (touch_upper_ + touch_lower_ + avg) / 3;
    344     touch_upper_ = (touch_upper_ + new_accepted) / 2;
    345     touch_lower_ = (touch_lower_ + new_accepted) / 2;
    346     touch_history_last_accepted_ = new_accepted;
    347     touch_history_direction_ = 0;
    348     touch_history_last_accepted_time_ = ev.GetEventTime();
    349   }
    350 }
    351 
    352 void ScaleGestureDetector::ResetTouchHistory() {
    353   touch_upper_ = std::numeric_limits<float>::quiet_NaN();
    354   touch_lower_ = std::numeric_limits<float>::quiet_NaN();
    355   touch_history_last_accepted_ = std::numeric_limits<float>::quiet_NaN();
    356   touch_history_direction_ = 0;
    357   touch_history_last_accepted_time_ = base::TimeTicks();
    358 }
    359 
    360 void ScaleGestureDetector::ResetScaleWithSpan(float span) {
    361   in_progress_ = false;
    362   initial_span_ = span;
    363   double_tap_mode_ = DOUBLE_TAP_MODE_NONE;
    364 }
    365 
    366 }  // namespace ui
    367